Can anti-cancer medication increase the risk of bone fracture?

The authors aimed to evaluate the risk of fractures and overall bone health following treatment with aromatase inhibitors.

Aromatase inhibitors (AIs) are a class of drug used to treat estrogen receptor positive breast cancer (ER+; breast cancer that is dependent on the hormone estrogen for growth). Their use, however, is associated with a decreased bone mineral density (BMD). BMD is used to determine a person's risk of bone fracture and osteoporosis.

The risk of fractures in women with no previous osteoporosis due to AIs has not been well studied.

The aim of this study was to determine the risk of bone fractures with the use of AIs.

A total of 497 women were evaluated for this study. Patients underwent bone scans and density tests at the start of the study and 3 years later. 122 women had osteoporosis (thinning of the bones) at the start of the study and were treated with both AIs and bisphosphonates (treatment to reduce bone loss). The remaining 267 women were treated with AIs only. 

The women who had no previous osteoporosis experienced a 3.5% decrease in spine bone density and a 2.1% decrease in hip bone density. Bone loss was significant only in patients under 65 years of age. 5.6% developed osteoporosis. Previous use of tamoxifen (Nolvadex, another type of estrogen blocker) had no impact on bone loss.

Over the 3 years of this study, 10% of the women who previously had osteoporosis developed at least 1 new bone fracture. This was more significant in older women (over 65). There was no significant decrease in bone density for any age group. 

The authors confirmed that aromatase inhibitors did induce some bone loss with a small fracture incidence in women without osteoporosis. This study also concluded that, in women with osteoporosis, bisphosphonates slowed bone loss but did not decrease fractures. 

Discuss your risk of bone fracture with your doctor.